This invention is directed to layered nonwoven materials comprising an abrasion resistant meltblown layer, which materials are suitable for use as outer covers for personal care articles such as disposable diapers and other disposable personal care articles, as well as medical garments, such as surgical gowns, medical drapes, and the like.
Layered nonwoven materials are widely used in a variety of applications, for example, such as components of absorbent articles such as disposable diapers, adult incontinence garments, and sanitary napkins, and in medical garments, such as surgical gowns, surgical drapes, sterilization wraps, and surgical face masks.
Layered nonwoven materials can be created for a variety of specific end uses by combining two or more nonwoven webs of different types. Thus, layered nonwoven materials have been developed to provide a barrier to penetration by contaminants such as microorganisms. Barrier nonwoven materials of this type typically include one or more microfibrous polymer layers, such as meltblown webs, combined with one or more layers of another type of nonwoven web, such as, for example, a spunbonded continuous filament fabric or a fabric of staple fibers. In known layered materials such as these, the outer layers function as strength reinforcing layers during use so as to protect the weaker meltblown web from excessive stresses and potential damage. Indeed, in order to protect the meltblown web from abrasion, it is normally disposed between two layers of another material, such as spunbond, which has a higher abrasion resistance, in a spunbond/meltblown/spunbond laminate. Such layered materials, thus, have outside spunbonded layers which are durable and an internal meltblown barrier layer which is porous but which, in combination with the spunbond layers, inhibits the strike through of liquids or the penetration of bacteria from the outside of the layered material to the inside.
The use of microfiber webs in applications where barrier properties are desired is known in the prior art. Microfibers are fibers having a denier per filament of from less than 0.006 to about 0.664. Microfiber webs are often referred to as meltblown webs as they are usually made by a meltblown process. It is generally recognized that the use of relatively small diameter fibers provides high repellency or filtration properties without undue compromise of breathability. Microfiber web fabrics made prior to now and intended for use as barriers in personal care articles and medical garments have been composites of microfiber webs laminated or otherwise bonded to spunbonded thermoplastic fiber webs, or films, or other reinforcing webs which provide the requisite strength. An important requirement for both nonwoven materials as well as personal care articles and medical garments is abrasion resistance. In the case of disposable diapers, resistance to surface abrasion is particularly important when a child is playing outdoors without clothing covering the diaper. Thus, an outer layer of a spunbonded fiber web, film or other reinforcing web is conventionally used to provide surface abrasion resistance in meltblown fiber products.
Personal care absorbent articles, such as disposable diapers, training pants, incontinence wear and feminine hygiene products, utilize nonwoven materials for many purposes such as liners, transfer layers, absorbent media, backings, and the like. For many such applications, the barrier properties of the nonwoven material play an important role. Disposable garments utilized for the absorption and containment of urine or other body exudates generally comprise a liquid pervious body side liner and a fluid impervious backing sheet or outer cover with an absorbent material disposed therebetween.
We have found that a spunbond material with a thin layer of meltblown fibers sprayed on it has about the same abrasion resistance as the spunbond itself. In view of the known generally lower resistance to abrasion of meltblown materials, this is, indeed, an unexpected and surprising finding. Much like a thin layer of paint protects a surface, compared to a very thick layer of paint which readily abrades, the thin meltblown layer acts as a protective coating, supported from below by the nonwoven web material it is coating. As a result of this discovery, meltblown fabrics, which have good barrier properties, making them particularly suited to use in personal care articles such as diapers, but which heretofore, due to their lack of strength and resistance to abrasion have, of necessity, been laminated between layers of nonwoven webs having the requisite strength, including resistance to abrasion, can now be used as the outer layer on such personal care articles, such as diaper outer covers. This, in turn, reduces the costs associated with production of these articles by eliminating the need for an additional outer nonwoven layer to protect the meltblown layer.
Nonwoven fabrics with improved abrasion resistance employing microfiber webs are taught by U.S. Pat. No. 4,774,125 which discloses a surface abrasion resistant material including a surface veneer of meltblown fibers having an average fiber diameter of greater than 8 microns (0.42 denier per filament for polypropylene) and in which 75% of the fibers have a fiber diameter of at least 7 microns (0.33 denier per filament for polypropylene) bonded to a meltblown core web. Such a material is indicated to be suitable for use as a medical fabric but, due to the lack of an absorbent layer, would not be suitable for use in personal care absorbent articles.
Accordingly, it is an object of this invention to provide an outer cover for personal care articles, such as diapers, having an outer meltblown layer which is resistant to abrasion, thereby permitting these items to be worn without additional layers, such as clothing, covering them to protect them from damage.